1. Field of the Invention
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98.
The invention relates to a method for finding the position of a communications device, and to a communications device for carrying out the method.
Future portable or car telephones will offer the capability, for example in the event of an accident or some other emergency situation, to send a short message automatically or manually to a service provider, with the position of the telephone also being transmitted at the same time.
Present-day traffic telematics systems provide for the last four known position information items, for example from a GPS receiver which can be installed in a motor vehicle, for example, to be transmitted to the service provider. A number of position information items have to be transmitted in order to confirm the direction in which the vehicle was last moving in order, for example, to allow a rescue vehicle to be sent onto the motorway in the correct direction, immediately and in the event of accidents on motorways.
However, this does not take account of the fact that the accuracy of the GPS position information fluctuates widely.
The invention is based on the object of specifying a method in order to allow more accurate position information relating to the communications device to be provided when required or in an emergency. Furthermore, a communications device for carrying out the method is intended to be provided.
Claim 1 contains a solution relating to the method of the set object. In contrast, claim 11 specifies a solution relating to an apparatus for the set object.
In the case of a method according to the invention for finding the position of a communications device, this device receives position data together with association position accuracies, in which case, in order to determine optimum positions, the communications device stores a number of such most recently received position data items whose position accuracy is better than a predetermined position accuracy.
Thus, in the case of the invention, position information which is subject to excessively high inaccuracy is not used any further and only position information with a high accuracy level is passed on to the service provider, in order to allow the communications device, or a person carrying it or a vehicle in which it is located, to be found more reliably when required or in an emergency.
In order to determine the optimum positions, the route on which the communications device is moving is expediently subdivided into sections. These may be predetermined journey distances or sections defined by predetermined time periods. An optimum position can then be determined for each of these sections so that, for example, four optimum positions can continuously be stored for four successive sections, for example in a memory in the form of a shift register. The number of buffer-stored optimum positions could also be greater than four.
Thus, to be more precise, a respective one of the optimum positions can be determined along in each case one predetermined journey distance, for example, or a respective one of the optimum positions can be determined in in each case one predetermined time period.
When determining the respective optimum positions in the respective sections (path or time sections), the predetermined position accuracy can also be changed, in order to obtain the best-possible optimum positions.
Thus, according to a refinement of the invention, within the predetermined journey distance or the predetermined time period, the predetermined position accuracy can be replaced by such a position accuracy from position data which are supplied later, which position accuracy is better than the predetermined position accuracy. This allows the best or the most accurate position in the respective path or time section to be found in a simple manner, which is then buffer-stored.
In this case, the predetermined position accuracy can be reset to a new (identical) initial value at the start of each predetermined journey distance or at the start of each predetermined time period, which initial value is then once again set to be somewhat greater than the best position accuracy from the previous section in order initially to allow an optimum position to be detected once again at all in the present section.
The initial value of the position accuracy can, of course, also be changed from section to section for a respective section, for example to match the actual geographical conditions.
If required, at least those optimum positions are transmitted to a service provider which have been determined for predetermined journey distances or predetermined time periods which have been completed.
However, in order to make the finding of the communications device when required or in an emergency even more reliable, it is also possible additionally to transmit to the service provider that optimum position which has been determined, when the requirement or the emergency occurred, for a predetermined journey distance or predetermined time period which had not yet been completed.
Furthermore, in another refinement of the invention, the most recently received position information when the requirement or emergency occurred is transmitted to the service provider as well, even if its position accuracy is poorer than the predetermined position accuracy. Even such position information with relatively poor position accuracy can provide a good indication of the actual location of the communications device, since this position information is associated with a position which is very close to the communications device.
A communications device which receives position data together with associated position accuracies contains a selection device for selecting a number of such most recently received position data items whose position accuracy is better than a predetermined position accuracy, as well as a memory device in order to store the position data selected in this way, as optimum positions. If an optimum position occurs in each case for successive path sections or time sections, then successive optimum positions can be passed through a memory which has a specific number of memory locations, for example being pushed through a memory having four memory locations, so that the last four or latest optimum positions are always available so that, if required or in an emergency, they can be transmitted to a service provider.
In this case, the communications device may have a switching device by means of which, when required or in an emergency, the memory device can be connected to a transmitter, via which the optimum positions are then transmitted to the service provider.
Furthermore, the selection device can set a time period for the selection of the position data as a function of control signals which can be produced once the communications device has travelled through predetermined journey distances, or once predetermined time periods have elapsed. The route of the communications device is thus subdivided by the control signals into the sections already mentioned above.
The position data together with the position accuracies may come directly from a satellite-aided radio navigation appliance (for example a GPS receiver), or may be determined by the communications device by measuring the delay time of signals coming from different base stations.